VITRINID^E. 137 



Subgenns PARMACOCHLEA, Smith, 1884. 



Animal as in Parmarion. Shell almost concealed, flattened, 

 oblong, having the nuclear portion in the form of a minute 

 Sigaretus-like shell projecting from beneath. 



Genus ASPIDELUS, Morelet, 1883. 



Animal limaciform, posteriorly dorsally carinated with a 

 caudal mucous pore ; shield moderate, gibbous, with slightly free 

 margin ; pulmonary orifice at the middle of the right margin of 

 the shield. 



Shell external, mytiliform, not spiral. W. Africa. 



Genus VITRINOZONITES, W. G. Binney, 1879. 



Shell elongated, submembranaceous. Animal with round 

 caudal mucous pore, bordered by a simple transversely grooved 

 rim, covered completely when closed, when open the cover raised 

 into a sharp carina. No appendiculate mantle-lobe. Marginal 

 teeth unicuspid, instead of bicuspid, as in Vitrina (PI. 29, 

 fig. 10). 



One species, mountains of E. Tennessee and W. North Caro- 

 lina. 



Genus VELIFERA, W. G. Binney, 1879. 



Shell subglobose, smooth, shining. Animal furnished with 

 accessory mantle processes covering most of the shell ; mucous 

 pore a simple slit, without horn-shaped process. Jaw smooth, 

 infeiiorly produced in the middle. Marginal teeth bifid (PI. 29, 

 fig. 11). 1 species. Costa Rica. 



Genus HELICARION, Ferussac, 1821. 



Shell Vitriniform, rounded oval, thin and fragile, covered 

 with a very thin epidermis ; whorls few, rapidly increasing, the 

 last much swollen ; aperture large, with simple, sharp peristome. 



Animal not entirely retractile within the shell ; mantle pro- 

 duced in front into two lobes upon the neck, with a posterior 

 lobe on the right side, partly covering the shell ; foot truncate 

 behind, with a dorsal projection and mucous pore, the sole 

 longitudinally divided into three parts. Marginal teeth bicuspi- 

 date (Dentition, PI. 29, fig. 12 ; jaw, PI. 29, fig. 13.) More than 



